Running 2k w/sp3 I went from 256 to 512 PC133 (on a PC100 system) memory and it caused 2 games to lockup. The MB is Soyo SY-6BA+IV with a Wintell BX440 chipset and a 450 PII. I ran a DOS based memory testing program on the box for 8-10 hours with 15 passes and they all passed.

The first 2 sticks are matched. The 3rd is a PC133 and the 4th is either a PC133 or 100. The board is only a 100 so I know the speed isn't a issue. The bios and Windows (I believe, since I have removed it since) does reconize the additional memory.

Is it just some incombatibility between the sticks? None are what I would call 'good' memory sticks (Crucial, Micron, Corsair etc.)

I new stick sside or dbside memory?.

Huh???????????

If you are asking if they are single side or double side, they are a mix I believe.

Yes I'am asking you if they are single side or double side memory it not good idea to mix them due to diff bank memory size.
You should be able to use 1,2,3 of DIMM socket with no probelm how ever if want to use the 4 DIMM socket you need swicth all your memory to registered DIMM.

When you said one is 133 and the other is 100. I'd stop right there. You've found your problem. Most systems have trouble when all the ram doesn't go at the same speed.

Hummm, in my experience running a mixture of PC100 & PC133 modules on a system that is only running on a FSB of 100Mhz is absolutely fine - remembering that PC133 means that the memory has been rated to run up to 133Mhz not 133Mhz only.

Boys or Girls my old BX can run mix PC100/PC133 but what I couldn't do was mix let say 8MBx16DS=128 with 16MBx8SS=128.
PC133 is backward compatible with PC100 spec.

Videobruce you would be better off pick up a piar of PC133 16MBx16DS=256 and saleing off the old 128 stick or keep them for some eles.

With RAM and the silly idiosynchrisies of different motherboards I've always just played it safe. I buy exactly the same chip from Micron every time, the only difference being that sometimes I'll buy say one 256 Meg stick, and one 512MB, but otherwise they're identical in every way. Micron makes pretty darn good RAM gold leads. Their RAM can be purchases at their RAM subcompany's website [url=www.Crucial.com]www.Crucial.com[/url] or from another vendor. The nice thing about crucial.com is you can select your motherboard and it'll only list RAM that works with it. That makes it pretty hard to screw things up, don't you think?
Just a suggestion for future practice,
Christian Blackburn